Abstract: Process for precipitating a mixed carbonate or mixed (oxy)hydroxide comprising nickel from an aqueous solution comprising a nickel salt, wherein such process is carried out in a vessel comprising (A) a vessel body, (B) one or more elements selected from draft tubes and guide vanes, (C) at least one stirrer whose pressure zone is in or between element(s) (B), and wherein the process comprises the step of simultaneously adding said solution comprising a nickel salt in or between element(s) (B) and a solution of alkali metal carbonate or hydroxide in or between or outside element(s) (B).